1. Field of the Invention
The present invention relates generally to computer storage devices and related software. More specifically, the invention relates to methods and devices for increasing the security of data stored in such devices.
2. Description of the Related Art
The design of highly secure hard disk drives is becoming increasingly important, particularly for applications that require high security levels, such as in the enterprise and government markets. Many hard disk drive (HDD) and other mass storage device manufacturers are attempting to make “security enhanced” hard disk drives to make data stored on them increasingly secure. In addition, standards groups and consortiums, such as the Trusted Computing Group (TCG), SNIA, IEEE, OASIS, and IETF, are working on solutions for secure and trusted storage.
Standard symmetric encryption techniques, such as AES and DES, and modes of encryption, such as ECB and CBC, that may be applied to specific portions of the disk drive, for example the portion sometimes referred to as the hidden partition (typically accessible only by the HDD firmware/controller) as well as to non-hidden segments, such as the user addressable space (UAS), have been found to be inadequate and may still allow for tampering. If one can modify or alter, for example, the hidden partition portion of a trusted storage device, a malicious user can easily compromise and fully control the device. Conventional encryption of a hidden and non-hidden partition is not sufficient to achieve high levels of security. Further enhancements to the security of trusted storage devices are always needed.
For example, one weakness in hidden partitions encrypted using conventional symmetric encryption is the ability to switch owners (an “owner” being any user or application allowed to access a specific partition) of a block of data such that the owner may now access a block of data in a partition that originally did not belong to that owner, while another owner may have access to the first owner's block. When this type of owner switch occurs, standard encryption techniques presently used for hidden partitions do not prevent access by users to unauthorized data.
The mode of encryption used to encrypt portions of a storage medium, in particular the hidden partition, is very important given that the overall performance of the HDD depends on it. For example, using Cipher-Block-Chaining (CBC) would require re-encrypting the entire hidden partition to make a single change to it. Another mode is ECB (Electronic Code Book) but this does not provide as strong security as CBC, although it may be more efficient. Another possibility is encrypting each block in the hidden partition using CBC, which may keep the performance drawback within reasonable limits. However, even using CBC on each sector in the hidden partition, attacks to the hidden partition are still possible, such as switching owners of a block as described above.
It would be desirable to have strong protection of hidden and non-hidden partition portions of a storage medium, even when the medium is not under strict control of the storage device controller. That is, when the storage media component of, for example, a hard disk device, is detached from the device and temporarily not under direct control of the device controller (firmware), the hidden partition of the storage media component should not be vulnerable to tampering or corruption.